Effects of Iodine on Growth and Iodine Absorption of Hydroponically Grown Tomato and Spinach

Abstract

The effects of I⁻ and IO₃⁻ on the growth and iodine absorption of tomato and spinach plants were investigated using a non-recirculating hydroponic system. Tomato and spinach plants were grown under 4 treatments; containing iodine I⁻ 0.1 mM, I⁻ 0.2 mM, IO₃⁻ 0.2 mM and 0 mM (control) for tomato, and I⁻ 0.05 mM, I⁻ 0.1 mM, IO₃⁻ 0.1 mM and 0 mM (control) for spinach. The results indicated that I⁻ treatment was more toxic to plants than IO₃⁻. I⁻ treatments reduced the absorption of nutrient solution. Spinach was more sensitive to iodine than tomato. Spinach grown with a higher I⁻ concentration showed symptoms of necrosis and leaf abscission. Based on these findings, tomato and spinach showed clear differences between their sensitivity to iodine. Further research will be required to achieve the final goal of using iodine as the disinfectant for hydroponic systems while avoiding toxicity to plants. In both species, iodine was found in high concentrations in leaf tissue. Therefore, a leafy vegetable like spinach might be a suitable crop to increase dietary iodine intake. Similarly, tomato fruits were found to accumulate iodine, thus, this crop might also contribute to achieving that objective.